The present invention is directed to bicycles and, more particularly, to a bicycle derailleur with a protective support.
A bicycle rear derailleur engages a driving chain on one of a plurality of sprockets mounted on the rear wheel hub. A conventional derailleur comprises a base member detachably fastened to the back end the frame, a chain guide for guiding the chain onto the plurality of sprockets, a movable member that pivotably supports the chain guide, and a link mechanism that movably supports the movable member relative to the base member. Such a derailleur is shown in Japanese Unexamined Patent Application No. 11-263282, for example.
Rear dropout portions are formed at the back end of the frame for installing the rear wheel hub. The base member may be supported on the frame in a cantilevered manner by screwing a bolt into a threaded opening formed below the hub mounting section of one of the frame dropout portions. Accordingly, the base member projects laterally outwardly from the frame. As used herein, the words “lateral” and “laterally” are to be interpreted according to the left and right directions in FIG. 4 (i.e., inward/outward from the side of the bicycle). The chain guide has a pair of vertically aligned pulleys that guide the chain onto one of the plurality of sprockets, wherein the chain guide is pivotably coupled to the moveable member so that the chain guide pivots around an axis that is substantially parallel to the hub axle. The chain guide is biased relative to the movable member in a direction that produces tension on the chain (typically clockwise when viewed laterally outwardly from the derailleur). The link mechanism may comprise a four-point link mechanism having a pair of links that move the movable member in the direction of the hub axle and diametrically outwardly as the chain guide moves closer to the sprockets. The inner cable of a Bowden cable assembly is fastened to the link mechanism such that pulling or releasing the inner cable using a shifter disposed on the handlebar causes the link mechanism to move the movable member and chain guide to engage the chain with a desired sprocket.
Since the laterally outwardly projecting derailleur is supported in a cantilevered manner at the back end of the frame, the base member and/or chain guide can bump into rocks, trees or the like when traveling over rough terrain such as mountainous terrain. This can cause the frame mounted components such as the base member to become bent or damaged, thus adversely affecting the operation of the derailleur.